1. Field of the Invention
The present invention is related to a liquid crystal display, and more particularly to a technique for improving an aperture ratio of the liquid crystal display.
2. Related Art
The quality of the liquid crystal display(LCD) is judged by some factors such as a contrast ratio which is ratio of brightness at voltage applied to the LCD to that at no applied voltage and a right-left viewing angle. Thus, there has been proposed an in-plane switching(IPS) mode LCD having superior contrast ratio and the right-left viewing angle.
In IPS mode LCD, both a pixel electrode and a counter electrode are formed on a lower substrate and an electric field between the pixel electrode and the counter electrode is parallel to a plane of the lower substrate.
In FIG. 1, the conventional IPS mode LCD is illustrated. A data line 1 is extended in a straight line and a U-shaped pixel electrode 2 is arranged parallel to the data line 1. A counter electrode 3 is an inverse U-shaped and interdigitated with respect to the pixel electrode 2. If voltage is applied, an electric field F1 is formed between the pixel electrode 2 and the counter electrode 3. The liquid crystal molecules are arranged responsive to the electric field F1. Since the length of the liquid crystal molecules in a minor axis is different from that in a major axis, the optical path is different according to the direction of an observer. Therefore, a screen color of the liquid crystal display is changed with respect to the viewing angle. That is, in case where the electric field F1 is generated, color of all screen of the liquid crystal must show white color. However, in the minor axis the screen color shows yellow and in the major axis the screen color is blue, thereby degrading picture quality of the LCD.
For improving the above mentioned defect, Hitachi Research had suggested a LCD with a bended pixel electrode and a bended counter electrode in Euro Display 96, in the title of "complete suppression of color shift in-plane switching mode LCDs with a multidomain structure obtained by undirectional rubbing", which is illustrated in FIGS. 2A and 2B. A data line 1 is in a form of a straight line. A pixel electrode 2a has a U-shaped bended form. A counter electrode 3a is an inverse U-shaped bended form and interdigitated with respect to the pixel electrode 2a. If voltage is applied, an electric field F2 is formed between the pixel electrode 2a and the counter electrode 3a. Since both the pixel electrode and the counter electrode are bended, director of the liquid crystal molecules is different in upper portion and lower portion centering around the bending line of the pixel electrode and the counter electrode. That is, multidomain is formed, so the color shift is suppressed.
However, since the data line is straight while the pixel electrode and the counter electrode are bended, there is formed a space H between the pixel electrode 2a and the data line 1. In the space H between the pixel electrode and the data line, is generated a parasitic electric field. For blocking the parasitic electric field, a black matrix 10 is located on a upper substrate as shown in FIG. 2B. The black matrix 10 reduces an aperture ratio of the LCD, so the power consumption is increased for obtaining a normal luminance.